Everytime i try to right click, it just places another one. I tried using a light switch but that didnt work either.

I just tested on SMP and single-player. It does turn on with a Modern Light Switch. Make sure you right-click the Modern Light with the Modern Light switch before placing the Switch on a block.

Note: You currently can't craft a Modern Light in survival until the crafting recipe is fixed.

It can only be powered with a light switch